This invention relates to a torque distribution apparatus for a 4 wheel driven vehicle equipped with a braking force controlling means for applying a braking force to an appropriate wheel to up-grade vehicle stability at cornering.
Recently developed and put into practical use are braking force controllers applying a braking force to an appropriate wheel to up-grade vehicle stability at cornering referring to influence of forces applied to a vehicle while cornering.
For example, the Japanese Patent Laid-open No. 70561/1990 disclosed a brake control device carrying out controls according to yaw rate, i.e., angular velocity of yawing which is rotary motion around plumb axis passing through a gravity center of a vehicle. In this technology, aimed yaw rate and real yaw rate of the vehicle are compared to determine vehicle dynamic characteristics as under steering or over steering against aimed yaw rate. And then a corrective braking force is applied to an inner wheel when judged as under steering or to an outer wheel when judged as over steering so that real yaw rate becomes equal to aimed yaw rate. Thus the vehicle running stability is up-graded.
Beside the above, disclosed for 4 wheel driven vehicles are various kinds of driving torque distribution devices, which can control torque distribution between front and rear wheels by appropriately controlling differential of front and rear wheel rotations in order to up-grade vehicle running stability.
Well known as a torque distribution device mentioned above is a limited slip center differential to be installed on a full time 4 wheel driven vehicle, wherein slippage of torque distribution clutch (transfer clutch) is controlled.
When the brake control device applies a braking force selectively to a wheel for up-grading vehicle stability in a 4 wheel driven vehicle equipped with the limited slip center differential, so strong engagement of the torque distribution clutch brings difficulty in precise application of the braking force as calculated. The reason is that each wheel can not rotate freely due to the strong engagement of the clutch that creates nearly mechanical connection of respective wheels.